It has been known to change the role of keys on a keyboard to produce more entries from fewer keys. For example U.S. Pat. No. 4,007,443 issued Feb. 8, 1977 to M. A. Bromberg et al. uses a set of twenty keys in four different modes selected by keys depressed by fingers on a hand holding a portable computer keyboard to produce alphameric input data. A similar technique is disclosed in U.S. Pat. No. 3,892,958 issued July 1, 1975 to C. C. Tung wherein two prefix or shift keys change the keyboard role to provide three times as many input possibilities from a set of keys in a portable computer. In U.S. Pat. No. 3,187,321 issued June 1, 1965 to S. L. Kameny, keyboard overlays with accompanying switching structure switch in different key operation modes and provide instructions to the operator showing what key operating modes are in use as different overlays are plugged in.
It has also been known that the number of keys on a keyboard for entry of alphabetic characters could be reduced to as few as seven keys by requiring two keystrokes per entry. This is disclosed in British Specification 1,417,849 published Dec. 17, 1975 and in U.S. Pat. No. 3,967,273 issued June 29, 1976 to K. C. Knowlton.
There are unsolved problems however created in systems having the keys so reduced on the keyboard. Thus with changing of key roles from time to time and the necessity to stroke keys in a particular sequence to select an entry, errors in operation are apt to occur because it is not always evident what the role of a particular key is. Furthermore, with modern computers, and particularly those operable in the alpha mode, there are so many entry choices available that it is difficult to memorize all the options that might be required for a particular use. This problem is even more acute in operation of portable hand held computers, where in general there is no access to an operating manual at the point of use. On hand held computers there is little room for visually accessible operating instructions for hundreds of input entry choices available from the keyboard. Furthermore, the art has been deficient in defining with unmistakable visual indicia instructions the sequential keystroke choices when multiple keystroke sequences are required for an entry. The aforesaid Knowlton U.S. Pat. No. 3,967,273 thus is ambiguous in identifying a keystroke sequence and requires complex mental choices in making sequential keystroke selections that are apt to cause error. Furthermore Knowlton is incapable of providing keychoice instructions for any changes in the key roles that cause different operations from any of the keys. Also it is difficult to view the indicia on a keyface or the keyboard or adjacent thereto when it is in use, and this slows down the selection process when the indicia are not fully memorized.
Accordingly it is a general objective of this invention to provide improved instructional indicia for entry of many different input commands and data characters, including full alphabet sets including punctuation, in the space available in hand held computers, and operable in computers that require a sequence of keystrokes per entry and that change the role of the keys on the keyboard.
Further objects, features and advantages are to be found throughout the following description, drawings and claims.